Jokic and Giannis have gone on the record saying that Euro basketball is "harder" than the NBA, and I can't believe I haven't seen anybody make this point, but their explanations only demonstrate that offense is harder and inadvertently point out that defense is easier. Really, all they're saying is that NBA spacing and rules make it easier for one player to dominate offense, but they are not actually explaining that the game is easier.
Luka seems to have had this right a couple years ago when he said scoring was easier in the NBA.